/*
 * Copyright (c) 1991, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *  @(#)queue.h 8.5 (Berkeley) 8/20/94
 * $FreeBSD: src/sys/sys/queue.h,v 1.32.2.6 2001/12/18 10:09:02 ru Exp $
 */

#ifndef _SYS_QUEUE_H_
#define _SYS_QUEUE_H_

/*
 * This file defines five types of data structures: singly-linked lists,
 * singly-linked tail queues, lists, tail queues, and circular queues.
 *
 * A singly-linked list is headed by a single forward pointer. The elements
 * are singly linked for minimum space and pointer manipulation overhead at
 * the expense of O(n) removal for arbitrary elements. New elements can be
 * added to the list after an existing element or at the head of the list.
 * Elements being removed from the head of the list should use the explicit
 * macro for this purpose for tmpimum efficiency. A singly-linked list may
 * only be traversed in the forward direction.  Singly-linked lists are ideal
 * for applications with large datasets and few or no removals or for
 * implementing a LIFO queue.
 *
 * A singly-linked tail queue is headed by a pair of pointers, one to the
 * head of the list and the other to the tail of the list. The elements are
 * singly linked for minimum space and pointer manipulation overhead at the
 * expense of O(n) removal for arbitrary elements. New elements can be added
 * to the list after an existing element, at the head of the list, or at the
 * end of the list. Elements being removed from the head of the tail queue
 * should use the explicit macro for this purpose for tmpimum efficiency.
 * A singly-linked tail queue may only be traversed in the forward direction.
 * Singly-linked tail queues are ideal for applications with large datasets
 * and few or no removals or for implementing a FIFO queue.
 *
 * A list is headed by a single forward pointer (or an array of forward
 * pointers for a hash table header). The elements are doubly linked
 * so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before
 * or after an existing element or at the head of the list. A list
 * may only be traversed in the forward direction.
 *
 * A tail queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or
 * after an existing element, at the head of the list, or at the end of
 * the list. A tail queue may be traversed in either direction.
 *
 * A circle queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or after
 * an existing element, at the head of the list, or at the end of the list.
 * A circle queue may be traversed in either direction, but has a more
 * complex end of list detection.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 *
 *
 *      SLIST LIST  STAILQ  TAILQ CIRCLEQ
 * _HEAD    + + + + +
 * _HEAD_INITIALIZER  + + + + +
 * _ENTRY   + + + + +
 * _INIT    + + + + +
 * _EMPTY   + + + + +
 * _FIRST   + + + + +
 * _NEXT    + + + + +
 * _PREV    - - - + +
 * _LAST    - - + + +
 * _FOREACH   + + + + +
 * _FOREACH_REVERSE - - - + +
 * _INSERT_HEAD   + + + + +
 * _INSERT_BEFORE - + - + +
 * _INSERT_AFTER  + + + + +
 * _INSERT_TAIL   - - + + +
 * _REMOVE_HEAD   + - + - -
 * _REMOVE    + + + + +
 *
 */

/*
 * Singly-linked List declarations.
 */
#define SLIST_HEAD(name, type)                  \
  struct name {                                 \
    struct type* slh_first; /* first element */ \
  }

#define SLIST_HEAD_INITIALIZER(head) \
  { NULL }

#define SLIST_ENTRY(type)                     \
  struct {                                    \
    struct type* sle_next; /* next element */ \
  }

/*
 * Singly-linked List functions.
 */
#define SLIST_EMPTY(head) ((head)->slh_first == NULL)

#define SLIST_FIRST(head) ((head)->slh_first)

#define SLIST_FOREACH(var, head, field) \
  for ((var) = SLIST_FIRST((head)); (var); (var) = SLIST_NEXT((var), field))

#define SLIST_INIT(head)        \
  do {                          \
    SLIST_FIRST((head)) = NULL; \
  } while (0)

#define SLIST_INSERT_AFTER(slistelm, elm, field)              \
  do {                                                        \
    SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field); \
    SLIST_NEXT((slistelm), field) = (elm);                    \
  } while (0)

#define SLIST_INSERT_HEAD(head, elm, field)         \
  do {                                              \
    SLIST_NEXT((elm), field) = SLIST_FIRST((head)); \
    SLIST_FIRST((head)) = (elm);                    \
  } while (0)

#define SLIST_NEXT(elm, field) ((elm)->field.sle_next)

#define SLIST_REMOVE(head, elm, type, field)            \
  do {                                                  \
    if (SLIST_FIRST((head)) == (elm)) {                 \
      SLIST_REMOVE_HEAD((head), field);                 \
    } else {                                            \
      struct type* curelm = SLIST_FIRST((head));        \
      while (SLIST_NEXT(curelm, field) != (elm))        \
        curelm = SLIST_NEXT(curelm, field);             \
      SLIST_NEXT(curelm, field) =                       \
          SLIST_NEXT(SLIST_NEXT(curelm, field), field); \
    }                                                   \
  } while (0)

#define SLIST_REMOVE_HEAD(head, field)                            \
  do {                                                            \
    SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field); \
  } while (0)

/*
 * Singly-linked Tail queue declarations.
 */
#define STAILQ_HEAD(name, type)                              \
  struct name {                                              \
    struct type* stqh_first; /* first element */             \
    struct type** stqh_last; /* addr of last next element */ \
  }

#define STAILQ_HEAD_INITIALIZER(head) \
  { NULL, &(head).stqh_first }

#define STAILQ_HEAD_INIT(head)             \
  do {                                     \
    (head).stqh_first = NULL;              \
    (head).stqh_last = &(head).stqh_first; \
  } while (0)

#define STAILQ_ENTRY(type)                     \
  struct {                                     \
    struct type* stqe_next; /* next element */ \
  }

/*
 * Singly-linked Tail queue functions.
 */
#define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)

#define STAILQ_FIRST(head) ((head)->stqh_first)

#define STAILQ_FOREACH(var, head, field) \
  for ((var) = STAILQ_FIRST((head)); (var); (var) = STAILQ_NEXT((var), field))

#define STAILQ_INIT(head)                      \
  do {                                         \
    STAILQ_FIRST((head)) = NULL;               \
    (head)->stqh_last = &STAILQ_FIRST((head)); \
  } while (0)

#define STAILQ_INSERT_AFTER(head, tqelm, elm, field)                       \
  do {                                                                     \
    if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL) \
      (head)->stqh_last = &STAILQ_NEXT((elm), field);                      \
    STAILQ_NEXT((tqelm), field) = (elm);                                   \
  } while (0)

#define STAILQ_INSERT_HEAD(head, elm, field)                        \
  do {                                                              \
    if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL) \
      (head)->stqh_last = &STAILQ_NEXT((elm), field);               \
    STAILQ_FIRST((head)) = (elm);                                   \
  } while (0)

#define STAILQ_INSERT_TAIL(head, elm, field)        \
  do {                                              \
    STAILQ_NEXT((elm), field) = NULL;               \
    *(head)->stqh_last = (elm);                     \
    (head)->stqh_last = &STAILQ_NEXT((elm), field); \
  } while (0)

#define STAILQ_LAST(head, type, field)                               \
  (STAILQ_EMPTY(head) ? NULL                                         \
                      : ((struct type*)((char*)((head)->stqh_last) - \
                                        __offsetof(struct type, field))))

#define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)

#define STAILQ_REMOVE(head, elm, type, field)                           \
  do {                                                                  \
    if (STAILQ_FIRST((head)) == (elm)) {                                \
      STAILQ_REMOVE_HEAD(head, field);                                  \
    } else {                                                            \
      struct type* curelm = STAILQ_FIRST((head));                       \
      while (STAILQ_NEXT(curelm, field) != (elm))                       \
        curelm = STAILQ_NEXT(curelm, field);                            \
      if ((STAILQ_NEXT(curelm, field) =                                 \
               STAILQ_NEXT(STAILQ_NEXT(curelm, field), field)) == NULL) \
        (head)->stqh_last = &STAILQ_NEXT((curelm), field);              \
    }                                                                   \
  } while (0)

#define STAILQ_REMOVE_HEAD(head, field)                                      \
  do {                                                                       \
    if ((STAILQ_FIRST((head)) = STAILQ_NEXT(STAILQ_FIRST((head)), field)) == \
        NULL)                                                                \
      (head)->stqh_last = &STAILQ_FIRST((head));                             \
  } while (0)

#define STAILQ_REMOVE_HEAD_UNTIL(head, elm, field)                  \
  do {                                                              \
    if ((STAILQ_FIRST((head)) = STAILQ_NEXT((elm), field)) == NULL) \
      (head)->stqh_last = &STAILQ_FIRST((head));                    \
  } while (0)

/*
 * List declarations.
 */
#define LIST_HEAD(name, type)                  \
  struct name {                                \
    struct type* lh_first; /* first element */ \
  }

#define LIST_HEAD_INITIALIZER(head) \
  { NULL }

#define LIST_ENTRY(type)                                          \
  struct {                                                        \
    struct type* le_next;  /* next element */                     \
    struct type** le_prev; /* address of previous next element */ \
  }

/*
 * List functions.
 */

#define LIST_EMPTY(head) ((head)->lh_first == NULL)

#define LIST_FIRST(head) ((head)->lh_first)

#define LIST_FOREACH(var, head, field) \
  for ((var) = LIST_FIRST((head)); (var); (var) = LIST_NEXT((var), field))

#define LIST_INIT(head)        \
  do {                         \
    LIST_FIRST((head)) = NULL; \
  } while (0)

#define LIST_INSERT_AFTER(listelm, elm, field)                               \
  do {                                                                       \
    if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)     \
      LIST_NEXT((listelm), field)->field.le_prev = &LIST_NEXT((elm), field); \
    LIST_NEXT((listelm), field) = (elm);                                     \
    (elm)->field.le_prev = &LIST_NEXT((listelm), field);                     \
  } while (0)

#define LIST_INSERT_BEFORE(listelm, elm, field)          \
  do {                                                   \
    (elm)->field.le_prev = (listelm)->field.le_prev;     \
    LIST_NEXT((elm), field) = (listelm);                 \
    *(listelm)->field.le_prev = (elm);                   \
    (listelm)->field.le_prev = &LIST_NEXT((elm), field); \
  } while (0)

#define LIST_INSERT_HEAD(head, elm, field)                          \
  do {                                                              \
    if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)     \
      LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field); \
    LIST_FIRST((head)) = (elm);                                     \
    (elm)->field.le_prev = &LIST_FIRST((head));                     \
  } while (0)

#define LIST_NEXT(elm, field) ((elm)->field.le_next)

#define LIST_REMOVE(elm, field)                                      \
  do {                                                               \
    if (LIST_NEXT((elm), field) != NULL)                             \
      LIST_NEXT((elm), field)->field.le_prev = (elm)->field.le_prev; \
    *(elm)->field.le_prev = LIST_NEXT((elm), field);                 \
  } while (0)

/*
 * Tail queue declarations.
 */
#define TAILQ_HEAD(name, type)                              \
  struct name {                                             \
    struct type* tqh_first; /* first element */             \
    struct type** tqh_last; /* addr of last next element */ \
  }

#define TAILQ_HEAD_INITIALIZER(head) \
  { NULL, &(head).tqh_first }

#define TAILQ_ENTRY(type)                                          \
  struct {                                                         \
    struct type* tqe_next;  /* next element */                     \
    struct type** tqe_prev; /* address of previous next element */ \
  }

/*
 * Tail queue functions.
 */
#define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)

#define TAILQ_FIRST(head) ((head)->tqh_first)

#define TAILQ_FOREACH(var, head, field) \
  for ((var) = TAILQ_FIRST((head)); (var); (var) = TAILQ_NEXT((var), field))

#define TAILQ_FOREACH_REVERSE(var, head, headname, field) \
  for ((var) = TAILQ_LAST((head), headname); (var);       \
       (var) = TAILQ_PREV((var), headname, field))

#define TAILQ_INIT(head)                     \
  do {                                       \
    TAILQ_FIRST((head)) = NULL;              \
    (head)->tqh_last = &TAILQ_FIRST((head)); \
  } while (0)

#define TAILQ_INSERT_AFTER(head, listelm, elm, field)                       \
  do {                                                                      \
    if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL)  \
      TAILQ_NEXT((elm), field)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
    else                                                                    \
      (head)->tqh_last = &TAILQ_NEXT((elm), field);                         \
    TAILQ_NEXT((listelm), field) = (elm);                                   \
    (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);                  \
  } while (0)

#define TAILQ_INSERT_BEFORE(listelm, elm, field)           \
  do {                                                     \
    (elm)->field.tqe_prev = (listelm)->field.tqe_prev;     \
    TAILQ_NEXT((elm), field) = (listelm);                  \
    *(listelm)->field.tqe_prev = (elm);                    \
    (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field); \
  } while (0)

#define TAILQ_INSERT_HEAD(head, elm, field)                            \
  do {                                                                 \
    if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)      \
      TAILQ_FIRST((head))->field.tqe_prev = &TAILQ_NEXT((elm), field); \
    else                                                               \
      (head)->tqh_last = &TAILQ_NEXT((elm), field);                    \
    TAILQ_FIRST((head)) = (elm);                                       \
    (elm)->field.tqe_prev = &TAILQ_FIRST((head));                      \
  } while (0)

#define TAILQ_INSERT_TAIL(head, elm, field)       \
  do {                                            \
    TAILQ_NEXT((elm), field) = NULL;              \
    (elm)->field.tqe_prev = (head)->tqh_last;     \
    *(head)->tqh_last = (elm);                    \
    (head)->tqh_last = &TAILQ_NEXT((elm), field); \
  } while (0)

#define TAILQ_LAST(head, headname) \
  (*(((struct headname*)((head)->tqh_last))->tqh_last))

#define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)

#define TAILQ_PREV(elm, headname, field) \
  (*(((struct headname*)((elm)->field.tqe_prev))->tqh_last))

#define TAILQ_REMOVE(head, elm, field)                                  \
  do {                                                                  \
    if ((TAILQ_NEXT((elm), field)) != NULL)                             \
      TAILQ_NEXT((elm), field)->field.tqe_prev = (elm)->field.tqe_prev; \
    else                                                                \
      (head)->tqh_last = (elm)->field.tqe_prev;                         \
    *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);                  \
  } while (0)

/*
 * Circular queue declarations.
 */
#define CIRCLEQ_HEAD(name, type)                \
  struct name {                                 \
    struct type* cqh_first; /* first element */ \
    struct type* cqh_last;  /* last element */  \
  }

#define CIRCLEQ_HEAD_INITIALIZER(head) \
  { (void*)&(head), (void*)&(head) }

#define CIRCLEQ_ENTRY(type)                       \
  struct {                                        \
    struct type* cqe_next; /* next element */     \
    struct type* cqe_prev; /* previous element */ \
  }

/*
 * Circular queue functions.
 */
#define CIRCLEQ_EMPTY(head) ((head)->cqh_first == (void*)(head))

#define CIRCLEQ_FIRST(head) ((head)->cqh_first)

#define CIRCLEQ_FOREACH(var, head, field)                     \
  for ((var) = CIRCLEQ_FIRST((head)); (var) != (void*)(head); \
       (var) = CIRCLEQ_NEXT((var), field))

#define CIRCLEQ_FOREACH_REVERSE(var, head, field)            \
  for ((var) = CIRCLEQ_LAST((head)); (var) != (void*)(head); \
       (var) = CIRCLEQ_PREV((var), field))

#define CIRCLEQ_INIT(head)                 \
  do {                                     \
    CIRCLEQ_FIRST((head)) = (void*)(head); \
    CIRCLEQ_LAST((head)) = (void*)(head);  \
  } while (0)

#define CIRCLEQ_INSERT_AFTER(head, listelm, elm, field)            \
  do {                                                             \
    CIRCLEQ_NEXT((elm), field) = CIRCLEQ_NEXT((listelm), field);   \
    CIRCLEQ_PREV((elm), field) = (listelm);                        \
    if (CIRCLEQ_NEXT((listelm), field) == (void*)(head))           \
      CIRCLEQ_LAST((head)) = (elm);                                \
    else                                                           \
      CIRCLEQ_PREV(CIRCLEQ_NEXT((listelm), field), field) = (elm); \
    CIRCLEQ_NEXT((listelm), field) = (elm);                        \
  } while (0)

#define CIRCLEQ_INSERT_BEFORE(head, listelm, elm, field)           \
  do {                                                             \
    CIRCLEQ_NEXT((elm), field) = (listelm);                        \
    CIRCLEQ_PREV((elm), field) = CIRCLEQ_PREV((listelm), field);   \
    if (CIRCLEQ_PREV((listelm), field) == (void*)(head))           \
      CIRCLEQ_FIRST((head)) = (elm);                               \
    else                                                           \
      CIRCLEQ_NEXT(CIRCLEQ_PREV((listelm), field), field) = (elm); \
    CIRCLEQ_PREV((listelm), field) = (elm);                        \
  } while (0)

#define CIRCLEQ_INSERT_HEAD(head, elm, field)             \
  do {                                                    \
    CIRCLEQ_NEXT((elm), field) = CIRCLEQ_FIRST((head));   \
    CIRCLEQ_PREV((elm), field) = (void*)(head);           \
    if (CIRCLEQ_LAST((head)) == (void*)(head))            \
      CIRCLEQ_LAST((head)) = (elm);                       \
    else                                                  \
      CIRCLEQ_PREV(CIRCLEQ_FIRST((head)), field) = (elm); \
    CIRCLEQ_FIRST((head)) = (elm);                        \
  } while (0)

#define CIRCLEQ_INSERT_TAIL(head, elm, field)            \
  do {                                                   \
    CIRCLEQ_NEXT((elm), field) = (void*)(head);          \
    CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head));   \
    if (CIRCLEQ_FIRST((head)) == (void*)(head))          \
      CIRCLEQ_FIRST((head)) = (elm);                     \
    else                                                 \
      CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm); \
    CIRCLEQ_LAST((head)) = (elm);                        \
  } while (0)

#define CIRCLEQ_LAST(head) ((head)->cqh_last)

#define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next)

#define CIRCLEQ_PREV(elm, field) ((elm)->field.cqe_prev)

#define CIRCLEQ_REMOVE(head, elm, field)                  \
  do {                                                    \
    if (CIRCLEQ_NEXT((elm), field) == (void*)(head))      \
      CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field);  \
    else                                                  \
      CIRCLEQ_PREV(CIRCLEQ_NEXT((elm), field), field) =   \
          CIRCLEQ_PREV((elm), field);                     \
    if (CIRCLEQ_PREV((elm), field) == (void*)(head))      \
      CIRCLEQ_FIRST((head)) = CIRCLEQ_NEXT((elm), field); \
    else                                                  \
      CIRCLEQ_NEXT(CIRCLEQ_PREV((elm), field), field) =   \
          CIRCLEQ_NEXT((elm), field);                     \
  } while (0)

#ifdef _KERNEL

/*
 * XXX insque() and remque() are an old way of handling certain queues.
 * They bogusly assumes that all queue heads look alike.
 */

struct quehead {
  struct quehead* qh_link;
  struct quehead* qh_rlink;
};

#ifdef __GNUC__

static __inline void insque(void* a, void* b) {
  struct quehead *element = (struct quehead*)a, *head = (struct quehead*)b;

  element->qh_link = head->qh_link;
  element->qh_rlink = head;
  head->qh_link = element;
  element->qh_link->qh_rlink = element;
}

static __inline void remque(void* a) {
  struct quehead* element = (struct quehead*)a;

  element->qh_link->qh_rlink = element->qh_rlink;
  element->qh_rlink->qh_link = element->qh_link;
  element->qh_rlink = 0;
}

#else /* !__GNUC__ */

void insque __P((void* a, void* b));
void remque __P((void* a));

#endif /* __GNUC__ */

#endif /* _KERNEL */

#endif /* !_SYS_QUEUE_H_ */
